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| Electret Microphone |
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| cosmarchy:
Hello all, I have a couple of circuits which require 3-pin electret microphones: The trouble is that I cannot find any 3-pin varieties here in the uk. Does anyone know of a reliable source for these? What is the difference (apart from the obvious ::)) between the 2 and 3 pin versions? |
| bob91343:
I think there is a discrepancy. An electret provides bias without a power supply. The circuits shown have a power supply, so they are probably not electret microphones, just ordinary condenser microphones that require power. Well, to be precise, not power but polarizing voltage. |
| floobydust:
Modern electret condenser mics are all two-wire, ground and signal. You could use one in your circuit, just short the tip+ring connection together. They have combined power and signal to save a wire. I think R1 is too low for a 9V feed, it is typically 10k-22k. The JFET in the mic is typically a 2SK596S with IDSS average 0.16mA if anyone wants to do math. You might need an extra RC filter for the mic power feed, any audio ripple on the 9V rail can get into the mic circuit and cause oscillations/feedback. Worse with battery power. edit: standard operating voltage is 2-3V for these mics, and you'd have to check the IDSS spec of the mic to get the best resistor value. It is not critical but the Internet is full of copycat errors. TI Electret Microphone Pre-Amplifier Reference Design uses 2V for 13.7k at 9V CUI mics specs 3V at 0.5mA max. |
| NiHaoMike:
A 3 wire microphone allows adjustment of sensitivity. https://sound-au.com/project93.htm |
| cosmarchy:
Thanks very much for your help guys, verymuch appreciated :D |
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